1. Field of the Invention
The present invention relates to a variable magnification image reproducing apparatus.
2. Description of the Prior Art
In a conventional variable magnification (power) copying machine, a desired copying magnification is selected or changed by the operator. Due to mechanical reasons, selection or change of magnification is prohibited during an interval in which a member for scanning an original image is not its home position. This is especially so where, when the scanning member is not in its home position prior to the initial scanning operation, this state is detected and the member is thereafter set in the home position. In such a case, selection or change of magnification is allowed after the scanning member is set in the home position. Therefore, a considerable period of time is required to complete selection or change of magnification. This results in an inefficient operation.
Selection or change of magnification is also prohibited after a copy start command is generated. More specifically, the operator first selects a magnification prior to a copying operation and then command, thereby starting the copying operation. Once the copy button is depressed to start the copying operation, correction or change of the selected magnification can only be performed after stopping the copying operation. This frequently results in production of an unwanted copy.
In a conventional variable magnification copying machine, the magnification can be varied by varying the scanning speed and stroke of a member for scanning an original in accordance with the magnification and the size of a transfer sheet. Furthermore, a lamp which generates heat such as a halogen lamp is used to illuminate the original to form an image thereof. Therefore, if the magnification is great and the size of the transfer sheet is small, the scanning speed is slow and the scanning stroke is short. For this reason, heat generated by the lamp may locally overheat the original base, causing a problem.
When a magnification is changed with the rotational frequency of a photosensitive drum remaining constant, the speed of the scanning member becomes slow. In the case of a copying machine of the original platen moving type wherein the copying speed is relatively slow from the beginning, the speed of the scanning member becomes still slower. In a conventional copying machine of the type wherein air is drawn from the top of the housing to exhaust air heated by the lamp, the cooling function is degraded to worsen the above problem.